Some current steering system designs have replaced the hydraulic power steering pump with electrically assisted systems based on fuel economy, modularity, engine independence, and environmental issues.
With electrically actuated or electrically assisted steering systems there is a significant servo mechanism design challenge associated with the need to maintain proper kinematical constraint, while at the same time, providing reasonable insulation from the drawbacks of tolerance stack up which may produce system lock up.
Although a successful servo mechanism design may appear to be a combination of basic “catalogue” mechanisms (e.g. ball-screw, gears, belts, various joints, etc.), the way these are used in combination represents an unmistakably cardinal feature of this art.
The current state of engineering meets these concerns by anticipating the stresses likely to be encountered by designing heavy-duty components. Needless to say, these designs are expensive to manufacture, have excessive performance challenges because of the increased inertia and friction, and add to the overall weight of the vehicle.
In most steering applications development of the actuator for power assist follows the synthesis and design of the suspension and steering linkages. Steering linkages could be steering the front wheels or rear wheels or both. Thus power assist steering may take the form of assisting front steering mechanism, rear steering mechanism or both. The steering linkage could also be connected to the steering wheel mechanically or via electronics that follow certain logic such as in “steer-by-wire” applications.